The present invention concerns a hydraulic pump, especially an oil pump, for a vehicle engine, provided with a pinion driven by the engine's crankshaft and with a centre-displaced ring-gear cooperating with it, and the pinion and the ring-gear are enclosed in a pump housing formed by an end cover fastened to the engine and another part secured thereto, of which at least the end cover has an aperture for the crankshaft.
The use of an oil pump in the form of a gearpump which is installed concentrically about, and is driven by, the engine's crankshaft is known for vehicle engines with pressure lubrication system. According to a usual design, the oil pump gear-wheel is placed in a separate pump housing which is bolted firmly to sealing contact with the outside of an end cover which is placed on one end of the engine block and creates together with the sides of the engine block part of the seal of the inside of the engine. This end-cover preferably forms a transmission cover which contains the engine's camshaft transmission and possibly also its balance-shaft transmission, both of which are driven by a drive placed on the end of the crankshaft. Outside the oil pump, there has usually been outermost on the end of the crankshaft a belt pulley for driving various auxiliary units such as cooling-water pump, generator and steering servo-pump. In such cases the end of the crankshaft passes through both the end-cover and the separate pump housing, which have cooperating machined planar contact surfaces which have to be sealed against leakage from the oil pressurised in the oil pump. The conventional version of the separate pump housing with all the feed and delivery ducts integrated in the pump housing has given the pump housing irregular contours. The seal between the contact planes is provided by an O-ring which is fitted in a groove in the contact plane of the pump housing and follows the irregular contours of the oil pump. This design results in relatively time-consuming fitting and removal of the oil pump, as a number of screws placed around the periphery of the pump housing are required for the fixing and sealing contact of the pump housing on the end-cover. Fitting a separate pump housing on the outside of the engine block end-cover also increases the engine's overall length. The irregular seal also entails leakage risks, as the O-ring may spring out of its groove while being fitted.
According to U.S. Pat. No. 4,382,756, fixing a cap in a pump housing by means of a grooved ring with circular cross-section is known per se in a hydraulic pump. In such cases the cap covers the shaft end and provides its bearing. To ensure good pump function, internal parts of the pump are spring-loaded towards the cap, which is thus pressed outwards and held against the locking ring.
Also known in another context is the fitting of a circular end-cap to a turbo-unit by means of a locking ring which is bevelled so as to press the cap inwards. The intention is to make it possible to fit the cap in the desired rotational position relative to the turbo-unit housing.
The automotive industry is increasingly endeavouring to simplify manufacture and assembly, but none of the previously known solutions for gearpumps installed about crankshaft ends achieves the desired simplicity in the case of an engine-mounted hydraulic pump.